As a variant, you could have it reverse the effect while in a party or raid (so the default action while solo is teleport and you hold Shift to portal, while the default action in a party/raid is to portal and you hold Shift to teleport):

i personally use spellcraft to manage my teleports and portals. its a little button that you can put anywhere, and you click and a column for teleports and next to it a column for the portals. its pimpin imo, and you can still be a nub and click teleport instead of portal, but thats what hearth stones are for right?

spellcraft also rebuys reagents (teleport, portal and arcane dust) as well as has other great mage functions, like those wispers you get when you get on my sheep, you bastards!

i have my blink spell but on where my bartender3 bar would be bar6, button one, this is right above my main actionbar, i then have it keybinded to the middle mouse scroll wheel, making it very easy to use the second i need 2, sinc my hand is on my mouse and all o.0